The present invention relates to fiber-optic communications networks, and more particularly, to optical network equipment such as optical amplifiers in which data may be stored for review and analysis.
Fiber-optic networks are used to support voice and data communications. In optical networks that use wavelength division multiplexing, multiple wavelengths of light are used to support multiple communications channels on a single fiber.
Optical amplifiers are used in fiber-optic networks to amplify optical signals. For example, optical amplifiers may be used to amplify optical data signals that have been attenuated by fiber spans and components in fiber-optic links. A typical amplifier may include erbium-doped fiber coils that are pumped with diode lasers. Raman amplifiers may also be used. Distributed Raman amplifiers include Raman-pumped transmission fiber. Discrete Raman amplifiers include Raman-pumped coils of fiber.
When channels are added and dropped from a link, the input power to an amplifier may change suddenly. This may cause gain transients in the amplifier unless the pump power of the amplifier is adjusted. Even when the pump power is adjusted appropriately to suppress transients, there may be small residual transient effects.
It may be desirable to analyze the transient control performance of an amplifier or to perform other performance measurements. For example, during troubleshooting operations or routine maintenance it may be desirable to investigate the performance of an amplifier in response to a given input power transient. This typically requires the use of ancillary test equipment such as high-speed power monitors and oscilloscopes. Moreover, some amplifier parameters such as pump drive currents cannot be readily measured, because there is no straightforward way to access these signals with the test equipment.
It is an object of the present invention to provide a way in which to gather information on the operation of an optical amplifier or other equipment by saving operating data such as sensor data and control data during equipment operation.
This and other objects of the invention are accomplished in accordance with the present invention by providing optical network equipment such as optical amplifiers for use in fiber-optic communications links in fiber-optic networks. The fiber-optic links may be used to carry optical data signals in a signal band associated with wavelength-division-multiplexing channels.
The optical amplifiers may include optically pumped rare-earth-doped fiber such as erbium-doped fiber or Raman-pumped fiber. Laser diode pumps may be used to optically pump the fiber to produce optical gain for the optical data signals in the signal band. The laser diode pumps may be adjusted in real time to prevent gain transients. An analog pump driver circuit may be used to provide a laser drive current for the laser diodes pumps. The analog pump driver circuit may be controlled by a digital-to-analog converter.
Optical taps and monitors may be used to measure the power of the optical data signals at appropriate locations along the main fiber path through the amplifier. Analog-to-digital converter circuitry may be used to digitize the measured power information.
A control unit may be used to control the operation of the optical amplifier. The control unit may store information on the operation of the amplifier such as the digital information used to control the digital-to-analog converters that are used to drive the pumps and the digital information from the optical monitor analog-to-digital converters. The control unit may also gather and store digital information from other sources within the amplifier. As the control unit processes digital information during operation of the amplifier, processed digital data is generated. This processed digital data may also be stored by the control unit.
The information that is stored by the control unit may be used during troubleshooting operations and during operations in which the optical amplifier or other network equipment is being set up or serviced.
Digital information may be collected on-demand by a user (e.g., in response to a digital data capture command) or when certain trigger criteria are satisfied. The user may be provided with an opportunity to establish desired trigger criteria and to otherwise customize the data capture process.